The former Australian representative told the veteran South African all-rounder, a former teammate of his at English county, Somerset, that he would be his first signing if he ever became coach of a Twenty20 team.

When Langer replaced Lachlan Stevens as coach of the Warriors and Scorchers in November, he was straight on the phone to Thomas, asking the 35-year-old to bring his experience Down Under.

He couldn't arrive in time for the first two games of the BBL campaign, games the Scorchers lost, but he has repaid Langer's faith in his ability since he first donned a bright orange shirt in round three.

Thomas, who played for the Adelaide Strikers in last summer's BBL, has taken 12 wickets in his six games this season at an impressive average of 10.80.

His economy rate is an outstanding 5.54 an over, and his best return has been 4-8.

It's form like that, together with that of opener Shaun Marsh, the competition's leading run-scorer with 328 runs at an average of 65.6, which has played a leading role in the Scorchers earning a home semi-final showdown against the Melbourne Stars at the WACA tonight.

The last time the two teams met in round 2 at the WACA, paceman Lasith Malinga destroyed the Scorchers, taking 6-7, the best figures in Australian domestic Twenty20 history, as the Shane Warne-captained Stars won by 10-wickets on the Duckworth/Lewis system.

Malinga won't be playing tonight as he is in the Sri Lankan ODI squad preparing for the third game at the Gabba on Friday.

Thomas said he and his teammates could not afford to take the Stars lightly, even without Malinga in the bowling attack.

"There is no doubt losing him (Malinga) does make a huge difference when you take into account what he did against us earlier this season," Thomas said.

"Saying that, they still have a decent bowling attack - Jackson Bird is coming off playing in a couple of Tests and he'll be confident, while James Faulkner is always a threat.

"Our batters will have to be on their game, for sure."

The Stars will also be missing Clint McKay and David Hussey through international commitments, but Thomas, whose nickname in England is "The Great Alfonso" (after a UK magician) because of his ability to bowl dot-balls at the death, said the visitors still posed a huge threat.

"The line-up is still a very dangerous one," he said.

"They will be well and truly up for it - Warney will certainly rev them up."